Solid-state metal carbonyls. Part 4.—An infrared and far-infrared study of M3(CO)12, M = Ru, Os

Abstract

The ν(CO) region of Ru₃(CO)₁₂ has been studied using single-crystal i.r.-reflectance in polarised light. Making use also of extant Raman data and of new low-temperature i.r. spectra, a detailed assignment is offered. Of the seven ν(CO) molecular modes located, only the two E′ modes, ν₁₆ and ν₁₇, show a rise in frequency from solution to solid.

In the δ(MCO), ν(M—C) region the major features of the spectra are readily accounted for on the basis of D_3h rules, the same being true of the complex region below 200 cm^–1. An essentially complete assignment is deduced. Lattice modes down to 21 cm^–1(Raman) and 24 cm^–1(i.r.) are found for Ru₃(CO)₁₂.